Turkish President Recep Tayyip Erdogan on Sunday was leading a tightly contested presidential election with most of the ballots counted, as he seeks a new mandate in the face of a revitalized opposition and weakening economy.
Erdogan needs at least 50% of the vote to win in the first-round presidential poll on June 24.
More than 56 million people were registered to vote at 180,000 ballot boxes across Turkey.
The former physics teacher, who has pledged to end what he calls Erdogan's "one-man rule", claimed the gathering attracted 5 million people, although no official estimates were available.
Polls for Turkey's landmark elections will open at 8am local time (05:00 GMT) on Sunday and close at 5pm (14:00 GMT).
The votes of Turkey's Kurdish minority will be especially crucial in the parliamentary poll. When two monitors suspected that hundreds of pre-stamped votes had been attempted to be cast, they started to record the incidents and the jostling in the ballot box between those committing the act and those trying to stop it.
Votes by Turks living overseas who cast their ballots in 60 countries at 123 embassies and consulates will be counted at the same time in the capital Ankara.
Meanwhile, President Recep Tayyip Erdoğan emerged as the victor in the presidential elections with a 54 percent lead with more than 80 percent of the country's ballot boxes counted.
If Erdogan wins both the presidency and control of Parliament, observers worry that Turkey could continue a slide from authoritarianism to outright dictatorship.
"People are getting more and more focused on the security of the vote and transparency of the elections", board member Sevan Camlidag told Middle East Eye. Few newspapers or other media openly criticize the government, and he has received far more election coverage than other presidential candidates.
However, in April, Turkish President Recep Tayyip Erdogan announced elections would be brought forward to June 24.
Polls heading into the vote suggested the ruling Islamist-rooted AK Party could lose parliamentary majority, which could hamper Erdogan's ability to power Turkey's new executive presidency.
The elections will complete Turkey's transition to a new executive presidential system, a move approved in a controversial referendum past year.
Supporters of the reforms argue that they will modernize the country, but opponents fear a possible authoritarian rule.
His main challenger is Muharrem Ince of the secularist Republican People's Party (CHP), while key Kurdish rival, Peoples' Democratic Party (HDP) representative Selahattin Demirtas, is campaigning from a prison cell where he has been held on terrorism charges regarding alleged links to Kurdish militants. Initiated by "Oy ve Ötesi" (Vote and Beyond) a few years ago, there are now dozens of such groups organizing tens and thousands of volunteers across the country - either to sign up as ballot observers from the lists of political parties or as independent observers, as permitted by Turkish election law.
Nationalist candidate Meral Aksener, nicknamed the "she-wolf" by her admirers, leads the Iyi party and is seen by many as the only viable alternative to Erdogan in a country that is becoming increasingly conservative.